A host device such a personal computer (PC) may access data on one or more mass storage devices via a Universal Serial Bus (USB) link. Such USB-linked mass storage devices may comprise a disk drive having a rotating storage media, or a solid state drive based upon semiconductor memory devices. Access by the PC to the data stored on the USB-connected mass storage device may employ a software driver in the PC for issuing commands to the mass storage device over the USB link. Such software drivers frequently use a block-only-transport (BOT) protocol that supports transfers of no more than 64 kilobytes (KB) per command. If an application wishes to transfer an amount of data greater than 64 KB, the driver breaks the transfer into a sequence of 64 KB transfers.
Each transfer of data between the PC and the mass storage device involves an amount of processing by the central processing unit (CPU) of the PC, to formulate and communicate a command to the mass storage device, followed by the transfer of the data to/from the mass storage device. During the time that the PC is preparing the command for transmission to the mass storage device, the mass storage device may be idle.
A USB mass storage device comprises one or more memory devices such a solid state or moving storage media, in addition to media controller and USB device controller functionality. The media controller and the USB device controller act as an interface between the USB connection with the host device, and the data storage device(s) use for data storage.
A USB host device such as, for example, a laptop, notebook, netbook or desktop PC; a personal digital assistant (PDA), a cellular telephone, or other intelligent device interfaces to a USB mass storage device through a host controller and host driver software. The USB host controller communicates with the USB device controller in the USB mass storage device over a multi-wire connection that includes power, ground, and data signals.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of ordinary skill in the art through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.